Vesicular monoamine transporter 2 (VMAT2) is an integral membrane protein that plays a critical role in aminergic synaptic transmission by replenishing depleted neurotransmitter stores in presynaptic vesicles. It works by harnessing a pre-existing proton gradient generated by V-type ATPase to couple the uptake of one cytoplasmic cationic amine with the efflux of two luminal protons. Substrates include serotonin, dopamine, norepinephrine, epinephrine, and histamine. The significance of VMAT2 is underscored by the phenomenal levels (~500 mM) to which it concentrates its substrates inside the synaptic vesicle and by its active role in sequestering several toxic compounds from the neuronal cytoplasm. Currently-prescribed therapeutics include the inhibitors reserpine [RES] and tetrabenazine [TBZ]. RES is used as a second-line agent to treat hypertension and psychosis; TBZ is approved to treat the uncontrolled movements in Huntington's disease and the tics in Tourette's syndrome. Despite such clinical and pharmacological significance, very little is known about the structural basis for transport, ion-dependence, substrate recognition, and inhibition. A VMAT2 crystal structure would provide the crucial information and likely revolutionize the field. The goal of this proposal is to gather the preliminary data required for such a pursuit: to express, purify, and obtain diffraction-quality crystals of a eukaryotic VMAT2 homologue. PUBLIC HEALTH RELEVANCE: Vesicular monoamine transporter 2 (VMAT2) plays a critical role in the overall process of synaptic transmission by replenishing depleted monoamine stores in synaptic vesicles. It is the target of the noncompetitive inhibitor tetrabenazine, clinically usd for symptomatic treatment of hyperkinetic disorders such as Huntington's disease, Tourette's syndrome, and tardive dyskinesia. Thus, understanding how this integral membrane works at the atomic level is a crucial goal.